1 == "查询账户"
2 == "存款"
3 == "取款"
0 == "退出"
n=[0,1,2,3]
for i in n:
    print(input("请选择服务种类："))
    if i ==1:
        print("当前余额:8000.00")
    elif i ==2:
        print(input("请输入取款数目:"))
        print("取款成功！请取现金！")
        print("当前余额:")
        break